1.编写程序，从指定目录文件开始，打印目录文件树(opendir, readdir)；

2.编写程序，打印指定目录文件下的所有的文件(readdir)，同时标识除文件的类型(stat)；

3.编写程序，在指定目录文件下创建一个新文件，删除一个指定文件，拷贝指定文件；-Write a program file from the specified directory, print directory file tree (the opendir, the fashion in which readdir) programming, print all the files under the specified directory file (readdir), while logo In addition to the file type (stat) programmingcreate a new file in the specified directory file, delete a specific file, copy the specified file